Method for protecting guanidino group and restoring the same

ABSTRACT

A guanidino group in an amino acid or a peptide can be protected with a specific group, i.e. pentamethylbenzensulfonyl, 2,4,6-trimethoxybenzenesulfonyl, 4-methoxy-2,3,5,6-tetramethylbenzenesulfonyl, 4-methoxy-2,6-dimethylbenzenesulfonyl or 4-methoxy-2,3,6-trimethylbenzenesulfonyl, and said group may easily be removed without affecting the amino acid or the peptide to be derived from the protected amino acid or peptide. Thus, the present invention is useful in the synthesis of peptides containing the guanidino group.

This invention relates in one aspect, to a method of producing peptidesinvolving the protection of a guanidino group and, in another aspect, toan arginine derivative or a salt thereof useful for the production ofpeptides.

For the production of a peptide using a starting compound containing aguanidino group ##STR1## (e.g. arginine), the guanidino group must beprotected beforehand. Protection of a guanidino group has heretoforebeen carried out by means of a nitro group or a tosyl group.

In such conventional processes, the elimination of the protective grouphas been possible only with poor yields. To remove the tosyl group, theelimination reaction must be conducted using anhydrous hydrogen fluorideunder severe conditions, which tend to decompose the other moieties ofthe peptide to give by-products and detract from the yield of thepeptide.

To overcome this disadvantage, the present inventors developed andpracticed a synthetic method involving the use of certainguanidino-protecting groups, such as p-methoxybenzenesulfonyl andmesitylenesulfonyl, which are easily removable with methanesulfonic acid(Japanese Patent Application Laid open No. 100030/1976). The subsequentstudies by the present inventors on the protection of guanidino led tothe discovery that

4-methoxy-2,6-dimethylbenzenesulfonyl, pentamethylbenzenesulfonyl,2,4,6-trimethoxybenzenesulfonyl,

4-methoxy-2,3,5,6-tetramethylbenzenesulfonyl and

4-methoxy-2,3,6-trimethylbenzenesulfonyl can be easily eliminated fromthe corresponding protected amino acids or peptide under mild acidicconditions.

Thus, an object of this invention is to provide a method for producing aguanidino-containing peptide which comprises protecting the guanidinogroup of a guanidino-containing starting material with a substitutedbenzenesulfonyl group of the following general formula (I): ##STR2##wherein R₁, R₃ and R₅ are methyl or methoxy, and R₂ and R₄ are hydrogenor methyl, provided that when R₃ is methyl, all of R₁, R₂, R₄ and R₅ aremethyl; when R₃ is methoxy and R₂ and R₄ are both hydrogen, R₁ and R₅are both methoxy; or when R₃ is methoxy and, at the same time, R₁ and R₅are both methyl, R₂ is hydrogen or methyl and R₄ is hydrogen or methyl,respectively, subjecting the protected compound to a peptide synthesisreaction and removing the protective group with an acid.

Another object of this invention is to provide an arginine derivative,inclusive of a salt thereof, which has the general formula (II):##STR3## wherein R₁ to R₅ are of the same meaning as defined in Formula(I) and R₆ is hydrogen or an α-amino-protecting group. A further objectof this invention is to provide 4-methoxy-2,3,6-trimethylbenzenesulfonylhalide.

In introducing a substituted benzenesulfonyl group of formula (I) intothe guanidino group of said guanidino-containing starting compound, theα-amino group of the guanidino-containing compound is previouslyprotected. Protection of the α-amino group can be accomplished by meansof a conventional protective group. For example, as the protective groupR₆ in general formula (II), there may be mentioned carbobenzoxy,p-nitrobenzyloxycarbonyl, p-methoxybenzyloxycarbonyl, t-butoxycarbonyl,t-amyloxycarbonyl, 9-fluorenylmethoxycarbonyl, isonicotinyloxycarbonyl,o-nitrophenylsulfenyl, 2-(p-biphenyl)isopropyloxycarbonyl, etc.,respectively as introduced in the per se known manner. Particularlyadvantageous are the compounds protected with carbobenzoxy ort-butoxycarbonyl.

Then, the guanidino group of the guanidino-containing compound with itsα-amino group thus protected is reacted with a substitutedbenzenesulfonyl group of general formula (I). This reaction isaccomplished by reacting about 1 to 5 equivalents, preferably about 1 to2 equivalents, of the substituted benzenesulfonyl compound (I) with theguanidino-containing compound. The sulfonyl group is usually employed asa halide.

The halide may be any of the chloride, fluoride, bromide and iodide. Inthis invention, 4-methoxy-2,3,6-trimethylbenzenesulfonyl chloride, oneof the substituted benzenesulfonyl groups (I), can be produced as acrystal, without the formation of isomer, by reacting2,3,5-trimethylanisole with chlorosulfonic acid.

Introduction of a substituted benzenesulfonyl group of formula (I) ispreferably carried out in the presence of a base. The base may forexample be sodium hydroxide, potassium hydroxide or lithium hydroxideand is employed in a proportion of about 1 to 10 equivalents, preferablyabout 1 to 5 equivalents, to each mole of guanidino-containing compound.Usually, this reaction is desirably conducted in a suitable solvent suchas water, acetone, dioxane, dimethyl-formamide or tetrahydrofuran or amixture of such solvents. This reaction is carried out at -10° C. to+25° C. and preferably at -5° C. to +10° C.

The resulting guanidino-containing compound with its guanidino groupprotected with a substituted benzenesulfonyl group of formula (I) issubjected, as it is in the free form or after being converted to thecyclohexylamine, dicyclohexylamine, sodium or other salt in the per seconventional manner, to the desired peptide condensation reaction.

In the context of this invention, the guanidino-containing compound withits guanidino group protected with a substituted benzenesulfonyl group(I) is any of the arginine derivatives of general formula (II) and saltsthereof.

The guanidino-containing compound with its guanidino grou protected witha substituted benzenesulfonyl group of general formula (I) is subjectedto a desired peptide condensation reaction in the conventional manner.As examples of such conventional manner, there may be mentioned thoseprocedures mentioned in M. Bodansky and M. A. Ondetti Peptide Synthesis,Interscience, New York, 1966, F. M. Finn and K. Hormann: The Proteins,Vol. 2, H. Nenrath, R. L. Hill (ed.), Academic Press Inc., New York,1976; Izumiya N. et al: Peptide Gosei (Peptide Synthesis), Maruzen(K.K.), 1975, etc., such as the azide process, chloride process, acidanhydride process, mixed acid anhydride process, DCC process, activatedester process, the process involving the use of Woodward's reagent K,carbodiimidazole process, redox process, DCC/HONB process and so on.

The peptide condensation reaction is now carried out. Then, theprotective group according to this invention is eliminated by means ofan acid. To remove this protective group, any of the conventional acidtreatments can be employed, such as the methanesulfonic acid process,trifluoromethanesulfonic acid process, etc. Moreover, in the case of themethod of this invention, the use of trifluoroacetic acid can beproposed as a new method of acid treatment. This elimination reactionproceeds very satisfactorily especially when it is conducted in thepresence of thioanisole or anisole.

As regards the amounts of said trifluoroacetic acid and said thioanisoleor anisole, it is advantageous to employ such amounts as are useful assolvents and are enough to remove the protective group. For example,they are used in a proportion of 1 to 10⁵ equivalents, preferably 1 to10³ equivalents, per mole of the compound having the protected guanidinogroup. This deprotecting reaction may be carried out in a solvent suchas acetic acid, chloroform or methylene chloride, and at a temperaturefrom about -10° C. to about +300° C., preferably at about +10° C. toabout +100° C.

The method according to this invention is applicable to the productionof any guanidino-containing peptide. As typical examples of suchpeptides, there may be mentioned physiologically active peptides such asDes-Gly¹⁰ -[D-Leu⁶ ]-LH-RH-ethylamide (Japanese Patent Publication No.14072/1978), Des-Gly¹⁰ -LH-RH-ethylamide (Japanese Patent PublicationNo. 24423/1978), Tuftsin (Nature 228, 672, 1970), Substance P,Kyotorphin, etc. Other peptides, such as MSH, ACTH, Glucagen-Secretin,Bradykinin, Dynorphin and α-Neoendorphin, as well as active fragments ofsuch peptides, can also be produced advantageously.

The substituted benzenesulfonyl group of general formula (I) inaccordance with this invention can be easily removed not only by theacid guanidino-deprotecting reactions heretofore known but by an acidtreatment under still milder conditions. For example, although a mildacid treatment with trifluoroacetic acid cannot be applied to theremoval of the hitherto-known guanidino-protecting groups, it can besuccessfully utilized in the elimination of the substitutedbenzenesulfonyl group of general formula (I).

In the conventional processes involving the protection of guanidino withp-methoxybenzenesulfonyl or mesitylenesulfonyl and a subsequentdeprotection with methanesulfonic acid after a peptide condensation, asuccinimide type side-reaction may take place if the peptide includes anasparagine or aspartic acid residue or an N O acyl rearrangementreaction may take place if a serine or thereonine residue is present. Inaccordance with this invention, even if the peptide contains these typesof amino acid residues, the protective group can be removed with a mildacid such as trifluoroacetic acid without inducing the above-mentionedside reactions.

This invention will hereinafter be described in detail by way of workingand test examples. In the present specifications, amino acids, peptides,protective groups, activated groups, etc. are sometimes designated bythe abbreviations recommended by IUPAC-IUB Commision on BiologicalNomeclature or those employed commonly in the field of art. Thefollowing is a partial list of such abbreviations.

pGlu: pyroglutamic acid

His: histidine

Trp: tryptophane

Ser: serine

Tyr: tyrosine

Leu: Leucine

Gly: glycine

Arg: arginine

Pro: proline

Lys: lysine

Gln: glutamine

Phe: phenylalanine

Met: methionine

Thr: threonine

(The above amino acids are L-amino acids unless otherwise indicated. TheD-acids will be specifically indicated. Gly is an exception).

Z: carbobenzoxy

Boc: t-butoxycarbonyl

HONB and ONB: N-hydroxy-5-norbornene-2,3-dicarboximide and its ester

HOBt: N-hydroxybenzotriazole

DCC: N,N'-dicyclohexylcarbodiimide

DCU: N,N'-dicyclohexylurea

H₂ /Pd: catalytic reduction

TFA: trifluoroacetic acid

CHA: cyclohexylamine

OTCP: 2,4,5-trichlorophenyl ester

OSu: N-hydroxysuccinimide ester

Et: ethyl

Further, in the present specification, the substituted benzenesulfonylgroups of general formula (I) will sometimes be designated by thefollowing abbreviations.

4-Methoxy-2,6-dimethylbenzenesulfonyl as MDS

4-Methoxy-2,3,6-trimethylbenzenesulfonyl as MtrPentamethylbenzenesulfonyl as Pme

2,4,6-Trimethoxybenzenesulfonyl as Tms

4-Methoxy-2,3,5,6-tetramethylbenzenesulfonyl as Tmo

EXAMPLE 1 (1) Synthesis of Z-Arg(MDS)-OH-CHA salt

In a mixture of 150 ml of 4 N-NaOH and 400 ml of acetone is dissolved46.2 g (0.15 M) of Z-Arg-OH at room temperature and the solution wascooled with ice. A solution of 70.7 g (0.30 M) of4-methoxy-2,6-dimethylbenzenesulfonyl chloride in 150 ml of acetone isadded dropwise to this solution over an hour. The mixture was stirred atroom temperature for 2 hours and solid citric acid was added to make thereaction solution acidic. The acetone was distilled off and theresulting oily substance was extracted with ethyl acetate. The ethylacetate layer was washed twice with water and the contemplated compoundwas extracted with aqueous NaHCO₃. The water layer was made acidic withcitric acid and the resulting oily substance was extracted with ethylacetate. The ethyl acetate layer was thoroughly washed with water anddried, and the ethyl acetate was distilled off under reduced pressure toobtain 63 g of oil. This oil was dissolved in 300 ml of ethyl acetate,and when cold, 14.3 ml of cyclohexylamine (CHA) was added. The mixturewas allowed to stand at room temperature overnight and the resultingcrystals were collected by filtration and recrystallized fromacetonitrile.

Yield, 48.0 g (52.8%); m.p. 140°-141° C.

Optical rotation [α]_(D) ²³ +5.7° (c=0.5, methanol), Thin layerchromatography (TLC): Rf₁ (CHCl₃ -methanol-acetic acid=9:1:0.5)=0.25

Elemental analysis: Calcd. for C₂₃ H₃₀ O₇ N₄ S.C₆ H₁₃ N: C, 57.50; H,7.15; N, 11.56; S, 5.29; Found: C, 57.23; H, 6.96; N, 11.66; S, 5.32.

(2) Synthesis of H-Arg(MDS)-OH

In 150 ml of methanol was dissolved 4.23 g (0.007 M) ofZ-Arg(MDS)-OH-CHA salt, and catalytic reduction was carried out in theconventional manner using palladium black as the catalyst. The catalystwas filtered off and the filtrate was concentrated under reducedpressure. To the residue was added water and the resulting crystals werecollected by filtration and recrystallized from water.

Yield 2.15 g (80.5%); m.p. 120°-122° C. (decomp.)

Optical rotation [α]_(D) ²³ -7.8° (c=0.7, methanol) TLC: Rf₂ (ethylacetate-pyridine-acetic acid-water=30:20:6:11)=0.16; Rf₄(n-butanol-ethyl acetate-water=1:1:1:1)=0.52

Elemental analysis: Calcd. for C₁₅ H₂₄ O₅ N₄ S.1/2H₂ O: C, 47.23; H,6.61; N, 14,69; S, 8.41; Found: C, 47.68; H, 6.58; N, 14.69; S. 8.47.

(3) Synthesis of Boc-Arg(MDS)-OH

In 1.65 ml of water was dissolved 1.12 g (0.003 M) of H-Arg(MDS)-OH, and0.63 ml (0.0045 M) of triethylamine was added when cold. To thissolution was added, under intense stirring, a solution of 793 mg (0.0033M) of t-butyl S-4,6-dimethylpyridimidine-2-ylthiolcarbonate in 1.65 mlof dioxane. The mixture was stirred at room temperature for 12 hours, atthe end of which time the dioxane was distilled off. The residue wasdiluted with water and the water layer was washed with ethyl acetate.The water layer was then made acidic with 6 N-HCl when cold and theresulting oil was extracted with ethyl acetate. The ethyl acetate layerwas washed twice with water and dried, and the ethyl acetate wasdistilled off under reduced pressure. The crystals formed as above aretreated with petroleum benzin, recovered by filtration andrecrystallized from ethyl acetate.

Yield 1.35 g (95.7%); m.p. 175°-176° C. (decomp.)

Optical rotation [α]_(D) ²⁶ +3.5° (c=0.5, methanol) TLC: Rf₁ =0.34

Elemental analysis: Calcd. for C₂₀ H₃₂ O₇ N₄ S: C, 50.83; H, 6.83; N,11.86; S, 6.79; Found: C, 50.96; H, 7.07; N, 11.56; S, 6.63.

TEST EXAMPLE

100 μmols of H-Arg(MDS)-OH were treated in:

(1) a mixture of trifluoroacetic acid (2 ml) and thioanisole (0.1 ml) at50° C. for 1 hour;

(2) a mixture of trifluoroacetic acid (2 ml) and thioanisole (0.1 ml) atroom temperature (21° C.) for 5 hours;

(3) a mixture of trifluoroacetic acid (2 ml) and anisole (0.1 ml) at 50°C. for 1 hour;

(4) a mixture of trifluoroacetic acid (2 ml) at 50° C. for 1 hour.

In each instance, the trifluoroacetic acid was distilled off underreduced pressure and the residue was dissolved in water and washed withether once. The mixture was weighed to take 100 ml and analyzed foramino acids. The yield of arginine was thus determined. The results areshown in Table 1.

                  TABLE 1                                                         ______________________________________                                                 Temperature                                                                              Time    Yield of Arg                                               (°C.)                                                                             (hrs.)  (%)                                               ______________________________________                                        TFA--thioanisole                                                                         50           1       93.2                                          (95:5)                                                                        TFA--thioanisole                                                                         21           5       89.3                                          (95:5)                                                                        TFA--anisole                                                                             50           1       79.4                                          (95:5)                                                                        TFA        50           1       78.0                                          ______________________________________                                         TFA: trifluoroacetic acid; amino acid analyzer: Hitachi Model 835        

EXAMPLE 2 Synthesis of Z-Arg(MDS)-Pro-NHEt

In 70 ml of methanol was dissolved 2.76 g (0.01 M) of Z-Pro-NHEtfollowed by addition of 1.90 g (0.01 M) of p-toluenesulfonic acid. Then,catalytic reduction was carried out in the conventional manner usingpalladium black as the catalyst. The catalyst was filtered off and thefiltrate was concentrated. The residue was dissolved in 50 ml ofdimethylformamide, and under ice cooling. 1.40 ml (0.01 M) oftriethylamine was added. Then, Z-Arg(MDS)-OH [prepared from 6.06 g (0.01M) of Z-Arg(MDS)-OH-CHA salt] and hydroxybenzotriazole (1.54 g, 0.01 M)were added and dissolved. To the solution was added 2.06 g (0.01 M) ofdicyclohexylcarbodiimide and the mixture was stirred for 24 hours. Theresulting urea was filtered off and the filtrate was concentrated invacuo. To the residue was added ethyl acetate and the ethyl acetatelayer was washed with aqueous NaHCO₃ and 0.2 N-HCl. The ethyl acetatewas distilled off under reduced pressure. The residue was treated withpetroleum benzin, and the resulting powdery solid was filtered off andpurified by silica gel chromatography using chloroform as eluent.

Yield 3.5 g (56.6%); m.p. 65°-67° C.

Optical rotation [α]_(D) ²³ -13.8° (c=0.5, dimethylformamide) TLC: Rf₁=0.47

Elemental analysis; Calcd. for C₂₉ H₄₂ O₇ N₆ S: C, 56.29; H, 6.84; N,13.58; S, 5.18; Found: C, 56.56; H, 6.81; N, 13.40; S, 4.93.

EXAMPLE 3 Synthesis of Z-Leu-Arg(MDS)-Pro-NHEt

In 70 ml of methanol was dissolved 3.16 g (0.0051 M) ofZ-Arg(MDS)-Pro-NHEt followed by addition of 969 mg (0.0051 M) ofp-toluenesulfonic acid. Then, catalytic reduction was carried out in theconventional manner using palladium black as the catalyst. The catalystwas filtered off and the filtrate was concentrated. The residue wasdissolved in 30 ml of dimethylformamide, followed by addition of 0.71 ml(0.0051 M) of triethylamine when cold and further addition of 2.40 g(0.0051 M×1.1) of Z-Leu-ONB. The mixture was stirred for 12 hours. Thesolvent was distilled off in vacuo and the residue was dissolved inethyl acetate. The ethyl acetate layer was washed with aqueous NaHCO₃and 0.2 N-HCl and, after drying, distilled off under reduced pressure.To the residue was added ether and the resulting precipitate wascollected by filtration and reprecipitated from ethyl acetate-ether.

Yield 2.5 g (67.0%); m.p. 95°-100° C.

Optical rotation [α]_(D) ²³ -22.0° (c=0.6, dimethylformamide TLC: Rf₁=0.50

Elemental analysis; Calcd. for C₃₅ H₅₃ O₈ N₇ S: C, 57.44; H, 7.31; N,13.40; S, 4.38; Found: C, 57.60; H, 7.29; N, 13.15; S, 4.28.

EXAMPLE 4 Synthesis of pGlu-His-Trp-Ser-Tyr-(D)Leu-Leu-Arg(MDS)-Pro-NHEt

In 50 ml of methanol was dissolved 732 mg (0.001 M) ofZ-Leu-Arg(MDS)-Pro-NHEt, and catalytic reduction was carried out in theconventional manner using palladium black as the catalyst. The catalystwas filtered off and the filtrate was concentrated. The residue wasdissolved in 10 ml of dimethylformamide. In this solution were dissolved816 mg (0.001 M) of pGlu-His-Trp-Ser-Tyr-(D)-Leu-OH and 717 mg (0.004 M)of HONB. The solution was cooled to -10° C. with ice-NaCl and, afteraddition of 412 mg (0.002 M) of dicyclohexylcarbodiimide, the mixturewas stirred at -10° C. for 3 hours, at 0° C. for 10 hours and at roomtemperature for 24 hours. The by-product urea was filtered off and thefiltrate was concentrated in vacuo. Ether was added to the residue andthe resulting precipitate was collected by filtration and reprecipitatedtwice from acetonitrile.

Yield 1.15 g (81.6%); m.p. 105°-110° C. (decomp.)

Optical rotation [α]_(D) ²³ -28.2° (c=0.6, dimethylformamide) TLC: Rf₂=0.20

Elemental analysis; Calcd. for C₆₈ H₉₃ O₁₅ N₁₆ S.H₂ O: C, 57.33; H,6.72; N, 15.73; S, 2.25; Found: C, 57.29; H, 7.18; N, 15.32; S, 2.02.

EXAMPLE 5 Synthesis of pGlu-His-Trp-Ser-Tyr-(D)-Leu-Leu-Arg-Pro-NHEt

In a mixture of 0.5 ml of thioanisole and 10 ml of trifluoroacetic acidwas dissolved 300 mg ofpGlu-His-Trp-Ser-Tyr-(D)-Leu-Leu-Arg(MDS)-Pro-NHEt and the solution wasleft standing at 50°-55° C. for 1 hour. The trifluoroacetic acid wasdistilled off under reduced pressure, ether was added to the residue andthe resulting precipitate was collected by filtration. The precipitatewas dissolved in a small amount of water and the solution was passedthrough a column (1.5×10 cm) of Amberlite IRA-410 (acetate-form). Theeffluent and washings were combined and directly passed onto a column(1.5×12 cm) of carboxymethyl-cellulose. The column was washed with 50 mlof water and elution was carried out by the linear gradient method usingwater (500 ml) and 0.15 M ammonium acetate (500 ml, pH 6.9). The mainfractions (240 to 390 ml) were pooled, lyophilized and dissolved in asmall amount of 1 N-acetic acid. The solution was passed through acolumn (2.5×120 cm) of Sephadex LH- 20 and elution was carried out withthe same solvent system as above. The main fractions (290-350 ml) werepooled and lyophilized.

Yield 120 mg

Optical rotation [α]_(D) ²³ -34.1° (c=0.4, 5% acetic acid)

TLC: Rf₃ (n-butanol-pyridine-acetic acid-water =30:20:6:24)=0.56

Amino acid analysis (acidolysis): His, 1.01(1); Arg+ethylamine,1.75(1+1); Trp, 0.90(1); Ser, 0.86(1); Glu, 1.05(1); Pro, 1.04(1); Leu,2.03(2); Tyr, 1.11(1); Average recovery 85.0%

EXAMPLE 6 Synthesis of pGlu-His-Trp-Ser-Tyr-Gly-Leu-Arg(MDS)-Pro-NHEt

Employing 476 mg (0.00065 M) of Z-Leu-Arg(MDS)-Pro-NHEt and 494 mg(0.00065 M) of pGlu-His-Trp-Ser-Tyr-Gly-OH, the contemplated compoundwere prepared by a procedure similar to that described in Example 4.

Yield 710 mg (80.9%), m.p. 135°-140° C. (decomp.)

Optical rotation [α]_(D) ²³ -26.7° (c=0.5, dimethylformamide); Rf₂ =0.16

Elemental analysis; Calcd. for C₆₄ H₈₅ O₁₅ N₁₆ S.H₂ O: C, 56.16; H,6.41; N, 16.38; S, 2.34; Found: C, 56.15; H, 6.71; N, 16.11; S, 2.18.

EXAMPLE 7 Synthesis of pGlu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-NHEt

Employing 300 mg of Arg(MDS)-Pro-NHEt, the contemplated compound wassynthesized by a procedure similar to that in Example 5.

Yield 122 mg

Optical rotation [α]_(D) ²³ -55.2° (c=0.5, 5% acetic acid) TLC: Rf₄=0.48 (Avicel)

Amino acid analysis (acidolysis): His, 1.02(1); Arg+ethylamine,1.83(1+1); Trp, 1.01(1); Ser, 0.81(1); Glu, 1.04(1); Pro, 1.00(1); Leu,1.03(1); Tyr, 1.03(1); Gly, 1.07(1), Average recovery, 90.0%

EXAMPLE 8 Synthesis of Boc-Arg(MDS)-Pro-Lys(Boc)-Pro-OH

In 50 ml of methanol was dissolved 590 mg (0.001 M) of oilyZ-Pro-Lys(Boc)-Pro-OMe as synthesized by serial condensation reaction ofH-Pro-OMe with Z-Lys(Boc)-ONB and Z-Pro-ONB, and catalytic reduction wascarried out in the conventional manner using palladium black as thecatalyst. The catalyst was filtered off and the filtrate wasconcentrated under reduced pressure. The residue was dissolved in 10 mlof dimethylformamide, followed by addition of 473 mg (0.001 M) ofBoc-Arg(MDS)-OH and 153 mg (0.001 M) of hydroxybenzotriazole. Themixture was reacted at room temperature for 12 hours. The resulting ureawas filtered off and the filtrate was concentrated in vacuo. The residuewas dissolved in ethyl acetate and the ethyl acetate layer was washedwith aqueous NaHCO₃ and 0.2 N-HCl and, after drying, the ethyl acetatewas distilled off under reduced pressure. The oily residue[Boc-Arg(MDS)-Pro-Lys(Boc)-Pro-OMe] was washed well with petroleumbenzin and dissolved in 10 ml of methanol, followed by addition of 2 mlof 1 N-NaOH when cold. The saponification reaction was carried out atroom temperature for 2 hours. Then, 2 ml of 1 N-HCl was added dropwisewhen cold and the reaction mixture was diluted with water. The resultingoily substance was extracted with ethyl acetate. The ethyl acetate layerwas washed with water and dried. The ethyl acetate was distilled offunder reduced pressure and the residue was treated with petroleum benzinand recovered by filtration. The resulting powder was reprecipitatedfrom ethyl acetate-ether.

Yield 530 mg (58.3%); m.p. 85°-90° C.

Optical rotation [α]_(D) ²⁶ -35.6° (c=0.5, dimethylformamide); TLC: Rf₁=0.33

Elemental analysis; Calcd. for C₄₂ H₆₈ O₁₂ N₈ S: C, 54.94; H, 7.58; N,12.21; S, 3.49; Found: C, 55.02; H, 7.65; N, 12.08; S, 3.63.

EXAMPLE 9 Synthesis ofBoc-Arg(MDS)-Pro-Lys(Boc)-Pro-Gln-Gln-Phe-Phe-Gly-Leu-Met-NH₂

In a mixture of trifluoroacetic acid (4.5 ml) and water (0.5 ml) wasdissolved 485 mg of Boc-Gln-Gln-Phe-Phe-Gly-Leu-Met-NH₂ [J. Bergmann, M.Bienert, H. Niedvich, B. Mehlis and P. Oehme, Experientia, 30, 401(1974)] and the solution was shaken at 10° C. for 20 minutes. After 0.5ml of 1 N-HCl was added, the mixture was distilled under reducedpressure. Then, ether was added to the residue and the precipitate wascollected by filtration and dried over sodium hydroxide. The resultingdry powder was dissolved in 15 ml of dimethylformamide followed by theaddition of 0.07 ml (0.0005 M) of triethylamine when cold. In themixture were dissolved 448 mg (0.0005 M) ofBoc-Arg(MDS)-Pro-Lys(Boc)-Pro-OH and 179 mg (0.001 M) of HONB. To thesolution was added 155 mg (0.0075 M) of dicyclohexylcarbodiimide and themixture was stirred for 24 hours. The by-product urea was filtered offand the filtrate was concentrated. Water was added to the residue, andthe resulting precipitate was collected by filtration and reprecipitatedtwice from ethanol.

Yield 500 mg (56.8%), m.p. 245°-247° C. (decomp.)

Optical rotation [α]_(D) ²⁶ -34.0° (c=0.5, dimethylformamide), TLC: Rf₂=0.83

Elemental analysis; Calcd. for C₈₃ H₁₂₆ O₂₀ N₁₈ S₂ : C, 56.64; H, 7.22;N, 14.32; S, 3.63; Found: C, 56.50; H, 7.15; N, 14.28; S, 3.73.

EXAMPLE 10 Synthesis ofH-Arg-Pro-Lys-Pro-Gln-Gln-Phe-Phe-Gly-Leu-Met-NH₂ (Substance P)

In a mixture of 1 ml of thioanisole and 10 ml of trifluoroacetic acid isdissolved 100 mg ofBoc-Arg(MDS)-Pro-Lys(Boc)-Pro-Gln-Gln-Phe-Phe-Gly-Leu-Met-NH₂ and thesolution was shaken at 50° C. for 2 hours. The trifluoroacetic acid wasdistilled off under reduced pressure, ether was added to the residue,and the resulting precipitate was collected by filtration, dried oversodium hydroxide in vacuo, and dissolved in a small amount of water. Tothe solution was added 3 ml of Amberlite IRA-410 (acetate-form) and themixture was shaken for a while. The resin was then filtered off and thefiltrate was lyophilized. The powdery lyophilizate was dissolved in asmall amount of 30% aqueous acetic acid. The solution was poured into acolumn (2.5×120 cm) of Sephadex G-25 and elution was carried out withthe same solvent system as above. The main fractions (240-280 ml) werepooled and lyophilized.

Yield 67 mg

Optical rotation [α]_(D) ²⁴ -80.7° (c=0.5, 5% acetic acid) TLC: Rf₃=0.53 (Avicel)

Amino acid analysis (acidolysis):

Lys, 0.99(1); Arg, 0.99(1); Glu, 2.03(2); Pro, 2.10(2); Gly, 0.99(1);Met, 0.99(1); Leu, 0.98(1); Phe, 1.96(2) Average recovery, 90.4%

EXAMPLE 11 Synthesis of Z-Pro-Arg(MDS)-OH

In 50 ml of dimethylformamide was dissolved 3.72 g (0.01 M) ofH-Arg(MDS)-OH, followed by addition of 1.40 ml (0.01 M) of triethylaminewhen cold and further addition of 4.5 g (0.011 M) of Z-Pro-ONB. Themixture was stirred at room temperature for 12 hours. To this reactionmixture was added 5 ml of acetic acid and the solvent was distilled offin vacuo. The residue was dissolved in ethyl acetate and the ethylacetate layer was washed twice with water. The ethyl acetate wasdistilled off under reduced pressure and the residue was treated withpetroleum benzin and filtered. The resulting powder was reprecipitatedfrom ethyl acetate-petroleum benzin.

Yield 5.6 g (93.3%); m.p. 75°-80° C.

Optical rotation [α]_(D) ²³ -16.0° (c=0.6, dimethylformamide); TLC: Rf₁=0.22

Elemental analysis; Calcd. for C₂₈ H₃₇ O₈ N₅ S: C, 55.71; H, 6.18; N,11.60; S, 5.31; Found: C, 56.18; H, 6.58; N, 11.26; S, 4.73.

EXAMPLE 12 Synthesis of H-Pro-Arg(MDS)-OH

In 100 ml of methanol was dissolved 5.4 g (0.009 M) ofZ-Pro-Arg(MDS)-OH, and catalytic reduction was carried out in theconventional manner using palladium black as the catalyst. The catalystwas filtered off, the filtrate was concentrated, and the residue wasdissolved in water and left standing in the cold. The resulting crystalswere collected by filtration.

Yield 2.80 g(66.0%); m.p. 173°-174° C. (decomp.)

Optical rotation [α]_(D) ²³ -15.8° (c=0.6, dimethylformamide); TLC: Rf₂=0.03, Rf₄ =0.46

Elemental analysis; Calcd. for C₂₀ H₃₂ O₆ N₅ S: C, 51.05; H, 6.86; N,14.88; S, 6.81; Found: C, 51.22; H, 6.95; N, 14.99; S, 6.86.

EXAMPLE 13 Synthesis of Z-Lys(Boc)-Pro-Arg(MDS)-OH

In 30 ml of dimethylformamide was dissolved 2.35 g (0.005 M) ofH-Pro-Arg(MDS)-OH, followed by additon of 0.7 ml of (0.005 M) oftriethylamine when cold and further addition of 2.80 g (0.005 M) ofZ-Lys(Boc)-OTCP. The mixture was stirred at room temperature for 12hours. After 3 ml of acetic acid was added to the above mixture, thedimethylformamide was distilled off in vacuo. The residue was dissolvedin ethyl acetate and the ethyl acetate layer was washed twice withwater. The solvent was distilled off under reduced pressure and theresidue was treated with ether. The resulting precipitate was collectedby filtration and reprecipitated from ethyl acetate-ether.

Yield 3.30 g (79.3%); m.p. 85°-90° C.

Optical rotation [α]_(D) ²³ -19.3° (c=0.6, dimethylformamide); TLC: Rf₁=0.25

Elemental analysis; Calcd. for C₃₉ H₅₇ O₁₁ N₇ S.1/2H₂ O: C, 55.70; H,6.95; N, 11.66; S, 3.81; Found: C, 55.77; H, 7.03; N, 11.77; S, 3.65.

EXAMPLE 14 Synthesis of Boc-Thr-Lys(Boc)-Pro-Arg(MDS)-OH

In 100 ml of methanol was dissolved 3.00 g (0.0036 M) ofZ-Lys(Boc)-Pro-Arg(MDS)-OH, and catalytic reduction was carried out inthe conventional manner using palladium black as the catalyst. Thecatalyst was filtered off and the filtrate was concentrated underreduced pressure. The residue was dissolved in 50 ml ofdimethylformamide and after addition of 0.50 ml (0.0036 M) oftriethylamine when cold, Boc-Thr-ONB [prepared from 877 mg (0.004 M) ofBoc-Thr-OH] was added. The mixture was stirred at room temperature for12 hours, 3 ml of acetic acid was then added and the solvent wasdistilled off in vacuo. The residue was dissolved in ethyl acetate andthe ethyl acetate layer was washed twice with water. The ethyl acetatewas distilled off under reduced pressure. The residue was treated withether and the resulting powdery solid was collected by filtration andreprecipitated from ethyl acetate-ether.

Yield 2.3 g (71.0%); m.p. 85°-90° C.

Optical rotation [α]_(D) ²³ -20.2° ;l (c=0.6, dimethylformamide); TLC:Rf₁ =0.14

Elemental analysis; Calcd. for C₄₀ H₆₆ O₁₃ N₈ S: C, 53.44; H, 7.40; N,12.46; S, 3.57: Found: C, 53.30;H, 7.65; N, 12.47; S, 3.36.

EXAMPLE 15 Synthesis of H-Thr-Lys-Pro-Arg-OH (Tuftsin)

In a mixture of 0.5 ml of thioanisole and 10 ml of trifluoroacetic acidwas dissolved 300 mg of Boc-Thr-Lys(Boc)-Pro-Arg(MDS)-OH, and thesolution was allowed to stand at 50° C. for 1 hour. The trifluoroaceticacid was distilled off under reduced pressure. The residue was treatedwith ether, and the resulting precipitate was collected by filtration,dried and dissolved in a small amount of water. The solution was shakenwith 10 ml of Amberlite IRA-410 (acetate-form) for 30 minutes. The resinwas then filtered off and the filtrate was lyophilized. The powderylyophilizate was dissolved in a small amount of water, and the solutionwas poured into a column (1.5×10 cm) of carboxymethyl-cellulose. Elutionwas carried out by the linear gradient method using water (300 ml) and0.2 M ammonium acetate (300 ml, pH 6.9). The main fractions (290 to 350ml) were pooled and lyophilized. The resulting powder was dissolved in 1N acetic acid, and the solution was poured into a column (2.5×120 cm) ofSephadex LH-20 and elution was carried out with the same solvent systemas above. The main fractions (270-310 ml) were pooled and lyophilized.

Yield 180 mg

Optical rotation [α]_(D) ²³ -63.1° (c=0.6, 5% acetic acid) TLC: Rf₃=0.22 (Avicel)

Amino acid analysis (acidolysis):

Lys, 1.00(1); Arg, 1.02(1); Thr, 1.01(1); Pro, 0.97(1); Averagerecovery, 92.0%

EXAMPLE 16 Synthesis of Boc-Tyr-Arg(MDS)-OH

In 30 ml of dimethylformamide was dissolved 1.91 g (0.005 M) ofH-Arg(MDS)-OH, followed by addition of 0.7 ml (0.005 M) of triethylaminewhen cold and further addition of 1.89 g (0.005 M) of Boc-Tyr-OSu. Themixture was stirred at room temperature for 12 hours. Then 5 ml ofacetic acid was added and the dimethylformamide distilled off in vacuo.The residue was dissolved in ethyl acetate and the ethyl acetate layerwas washed twice with water. The ethyl acetate was distilled off underreduced pressure. The residue was treated with ether and the resultingprecipitate was collected by filtration and reprecipitated from ethylacetate-ether.

Yield 2.70 g (84.9%); m.p 85°-90° C.

Optical rotation [α]_(D) ²³ +0.6° (c=0.5, dimethylformamide); TLC: Rf₁=0.14

Elemental analysis; Calcd. for C₂₉ H₄₁ O₉ N₅ S: C, 54.79; H, 6.50; N,11.02; S, 5.04; Found: C, 54.94; H, 7.01; N, 10.66; S, 4.54.

EXAMPLE 17

Synthesis of H-Tyr-Arg-OH (Kyotorphin)

In a mixture of 0.5 ml of thioanisole and 10 ml of trifluoroacetic acidwas dissolved 300 mg of Boc-Tyr-Arg(MDS)-OH, and the solution was leftstanding at 50°-55° C. for 1 hour. The trifluoroacetic acid wasdistilled off under reduced pressure. The residue was treated withether, and the resulting precipitate was collected by filtration anddissolved in a small amount of water. The solution was shaken with 10 mlof Amberlite IRA-410 (acetic-form) for 30 minutes. The resin wasfiltered off and the filtrate was lyophilized. The powdery lyophilizatewas dissolved in a small amount of water and poured into a column(1.5×10 cm) of carboxymethylcellulose. Elution was carried out by thelinear gradient method using water (300 ml) and 0.1 M ammonium acetate(300 ml, pH 6.9). The main fractions (100 to 150 ml) were pooled andlyophilized. The powdery lyophilizate was dissolved in a small amount of1 N-acetic acid. The solution was poured into a column (2.5×120 cm) ofSephadex LH-20 and elution was carried out with the same solvent systemas above. The main fractions were pooled and lyophilized.

Yield 150 mg

Optical rotation [α]_(D) ²¹ -17.6° (c=0.4, water) TLC: Rf₃ =0.45(Avicel) Amino acid analysis (acidolysis):

Arg, 1.06(1); Tyr, 0.94(1); Average recovery, 90.6%

REFERENCE EXAMPLE 1 Synthesis of pentamethylbenzenesulfonyl chloride

In 500 ml of dichloromethane was dissolved 17.8 g of pentamethylbenzeneand the solution was cooled to -5°˜-10° C. A solution of 24 ml ofchlorosulfonic acid in 400 ml of dichloromethane was added dropwise, andthe mixture was allowed to stand at room temperature. The reactionmixture was poured into ice-5% aqueous sodium hydrogen carbonate. Theorganic layer was washed with water and dried over magnesium sulfate.Removal of the solvent by distillation leaves crystals which werecollected by filtration and recrystallized from n-hexane. Yield 27.7 g(93.5%), m.p. 80°-81° C.

Elemental analysis for C₁₁ H₁₅ O₂ SCl; Calcd.: C, 53.54; H, 6.13; S,13.00; Cl, 14.37; Found: C, 53.78; H, 6.09; S, 13.00; Cl, 14.39.

REFERENCE EXAMPLE 2 Synthesis of 2,4,6-trimethoxybenzenesulfonylchloride

In 500 ml of dichloromethane is dissolved 5.05 g of1,3,5-trimethoxybenzene and the solution was cooled to -5°˜-10° C. Asolution of 6 ml of chlorosulfonic acid in 400 ml of dichloromethane wasadded dropwise, and the mixture was allowed to stand at roomtemperature. The reaction mixture was then treated as in ReferenceExample 1. The resulting product was crystallized from carbontetrachloride and filtered. Yield 610 mg (6.3%), m.p. 126°-129° C.

Elemental analysis for C₉ H₁₁ O₅ SCl; Calcd.: C, 40.53; H, 4.16; S,12.02; Cl, 13.30; Found: C, 40.79; H, 4.16; S, 11.84; Cl, 13.28.

EXAMPLE 18 (1) Synthesis of Z-Arg(Pme)-OH.CHA

In a mixed solution of 33 ml of 4 N-NaOH and 130 ml of acetone wasdissolved 10.0 g of Z-Arg-OH, and the mixture is ice-cooled. A solutionof 14.0 g of pentamethylbenzenesulfonyl chloride in acetone (30 ml) wasadded dropwise and the mixture was stirred for 2 hours. The reactionmixture was acidified with citric acid, the solvent was distilled offand the residue was extracted with ethyl acetate. The ethyl acetatelayer was extracted with aqueous NaHCO₃ and the extract was acidifiedwith citric acid and extracted with ethyl acetate again, followed bydrying over anhydrous sodium sulfate. After the solvent was distilledoff, 3.55 ml of cyclohexylamine was added to the residue and theresultant salt was crystallized from ethyl acetate and collected byfiltration.

Yield 13.3 g (66.4%), m.p. 173°-175° C., [α]_(D) ²³ +5.8° (c=1.27,methanol)

Elemental analysis for C₃₁ H₄₇ O₆ N₅ S; Calcd.: C, 60.26; H, 7.67; N,11.34; S, 5.19; Found: C, 60.15; H, 7.84; N, 11.25; S, 5.30

(2) Synthesis of H-Arg(Pme)-OH

To 1.24 g of Z-Arg(Pme)OH-CHA was added 3 ml of 1 N-H₂ SO₄, and themixture was extracted with ethyl acetate. The solvent was distilled offand the residue was dissolved in 30 ml of methanol. Catalytic reductionwas carried out in the presence of Pd black as catalyst. The catalystwas filtered off, the solvent distilled off, and the residuecrystallized by addition of ether and filtered.

Yield 0.77 g (97.8%), m.p. 153°-156° C., [α]_(D) ²³ -5.5° (c=0.91,methanol)

Elemental analysis for C₁₇ H₂₈ O₄ N₄ S.1/2H₂ O; Calcd.: C, 51.89; H,7.43; N, 14.24; S, 8.15; Found: C, 51.60; H, 7.74; N, 13.80; S, 8.12.

EXAMPLE 19 (1) Synthesis of Z-Arg(Tms)-OH

In a mixed solution of 2.5 ml of 4 N-NaOH and 10 ml of acetone isdissolved 0.77 g of Z-Arg-OH and the solution was ice-cooled. A solution(3 ml) of 1.0 g of 2,4,6-trimethoxybenzenesulfonyl chloride in acetonewas added dropwise and the mixture was stirred for 2 hours. The reactionmixture was made acidic with citric acid, the solvent distilled off, andthe residue saturated with NaCl and extracted with ethyl acetate. Theextract was dried over anhydrous sodium sulfate and the solvent wasdistilled off. To the residue was added ether and the resulting powderwas collected by filtration. The powder was dissolved in 10 ml ofchloroform, subjected to silica gel column (4×10 cm) chromatography,elution being carried out with chloroform-methanol-acetic acid(9:0.7:0.35). The fractions from 110 ml to 210 ml were pooled,concentrated and precipitated from ether and the resulting powder wasrecovered by filtration.

Yield 250 mg (18.0%), m.p. 89°-93° C., [α]_(D) ²³ +0.8° (c=0.50,methanol)

Elemental analysis for C₂₃ H₃₀ O₉ N₄ S.H₂ O; Calcd.: C, 49.63; H, 5.80;N, 10.07; S, 5.76; Found: C, 49.67; H, 5.57; N, 9.87; S, 5.81.

(2) Synthesis of H-Arg(Tms)-OH

Z-Arg(Tms)-OH (150 mg) was catalytically reduced in methanol using Pdblack as catalyst. The catalyst was filtered off and the solvent wasdistilled off. To the residue was added ether and the resulting powderwas collected by filtration.

Yield 105 mg (89.1%), m.p. 115°-120° C., [α]_(D) ²³ -8.9° (c=0.60,methanol)

Elemental analysis for C₁₅ H₂₄ O₇ N₄ S.CH₃ OH; Calcd.: C, 44.02; H,6.47; N, 12.84; S, 7.35; Found: C, 43.55; H, 6.33; N, 12.84; S, 6.99.

EXAMPLE 20 (1) Synthesis of 2,3,5,6-tetramethylanisole

In 150 ml of DMSO were dissolved 15.0 g of 2,3,5,6-tetramethylphenol and28 ml of methyl iodide. Under ice-cooling 6.3 g of 60% sodium hydride inoil was added, and the mixture was stirred at room temperature for 1hour. The excess sodium hydride was decomposed with MeOH and afteraddition of water extraction with ether was carried out. The extract wasdried over sodium sulfate. Removal of the solvent by distillation leavescrystals which were recrystallized from MeOH.

Yield 10.2 g (62.1%), m.p. 45°-47° C.

(2) 4-Methoxy-2,3,5,6-tetramethylbenzenesulfonyl chloride

In 600 ml of dichloromethane was dissolved 10.0 g of2,3,5,6-tetramethylanisole, followed by addition of a solution (400 ml)of 12 ml of chlorosulfonic acid in dichloromethane at -5°˜-10° C. Themixture was kept stirred for 2 hours and the reaction mixture was pouredinto ice-5% aqueous NaHCO₃. The organic layer was washed with water anddried over magnesium sulfate. The solvent was distilled off and theresidue was crystallized from n-hexane and filtered.

Yield 10.0 g (62.5%), m.p. 58°-59° C.

Elemental analysis for C₁₁ H₁₅ O₃ SCl; Found: C, 50.52; H, 5.56; S,11.92; Cl, 13.42.

(3) Synthesis of Z-Arg(Tmo)-OH.CHA

In a mixture of 6 ml of 4 N-NaOH and 25 ml of acetone was dissolved 1.85g of Z-Arg-OH and the solution was ice-cooled. A solution (100 ml) of2.50 g of 4-methoxy-2,3,5,6-tetramethylbenzenesulfonyl chloride inacetone was added and the mixture was stirred for 1 hour. Aqueous citricacid was added, the solvent was distilled off, and the desired productextracted with ethyl acetate and dried over anhydrous sodium sulfate.The solvent was distilled off and 0.58 ml of cyclohexylamine was added.The resulting product was crystallized from ether, filtered and dried.

Yield 2.40 g (63.1%), m.p. 127°-129° C., [α]_(D) ²³ +5.9° (c=0.84,methanol)

Elemental analysis for C₃₁ H₄₇ O₇ N₅ S; Calcd.: C, 58.74; H, 7.48; N,11.05; S, 5.06; Found: C, 58.84; H, 7.30; N, 11.25; S, 5.06.

(4) Synthesis of H.Arg(Tmo)-OH

In 40 ml of ethyl acetate was suspended 2.0 g of Z-Arg(Tmo)-OH.CHA,followed by addition of 4 ml of 1 N-sulfuric acid. The mixture wasshaken well and washed with water and the solvent distilled off. Theresidue was dissolved in 40 ml of methanol and catalytic reduction wascarried out in the presence of Pd black as catalyst. The catalyst wasfiltered off and the solvent was distilled off. To the residue was addedether and the resulting powder was collected by filtration and dried.

Yield 1.20 g (92.7%), m.p. 150°-153° C., [α]_(D) ²³ -4.5° (c=0.92,methanol)

Elemental analysis for C₁₇ H₂₈ O₅ N₄ S.1/2H₂ O; Calcd.: C, 49.86; H,7.14; N, 13.68; S, 7.83; Found: C, 50.38; H, 7.57; N, 13.48; S, 7.60.

TEST EXAMPLE

Each of the N^(G) -protected arginine (approx. 20 mg) was dissolved in 2ml of trifluoroacetic acid-thioanisole (9:1) and the solution wasallowed to stand at 50° C. for 1 or 4 hours. A 100 μl portion of thesolution was taken, made up to 10 ml and analyzed for arginine. Theresults are shown in Table 2.

                  TABLE 2                                                         ______________________________________                                                   Temperature        Yield of Arg                                               (°C.)                                                                           Time (hrs.)                                                                             (%)                                             ______________________________________                                        H--Arg(Pme)--OH                                                                            50         1         64                                                                  4         89                                          H--Arg(Tms)--OH                                                                            50         1         90                                                                  4         91                                          H--Arg(Tmo)--OH                                                                            50         1         30                                                                  4         81                                          ______________________________________                                    

EXAMPLE 21 (1) Synthesis of Boc-Tyr-Arg(Pme)-OH

In 20 ml of tetrahydrofuran was dissolved 790 mg of H-Arg(Pme)-OH. Then,0.34 ml of triethylamine and Boc-Tyr-ONB (prepared from 0.57 g ofBoc-Tyr-OH, 0.40 g of HONB and 0.50 g of DCC) added when cold and themixture was stirred at room temperature for 15 hours. The solvent wasdistilled off and the residue was made acidic with citric acid andextracted with ethyl acetate. The ethyl acetate layer was washed withwater and the solvent was distilled off. The residue was dissolved inchloroform and subjected to silica gel column (4×6 cm) chromatography.Elution was carried out with 5% MeOH/CHCl₃. The fractions containing thedesired product were pooled, concentrated and precipitated from etherand the resulting powder was recovered by filtration.

Yield 690 mg (51.8%), m.p. 136°-139° C., [α]_(D) ²³ -15.0° (c=0.5,dimethylformamide)

Elemental analysis for C₃₁ H₄₅ O₈ N₅ S.H₂ O; Calcd.: C, 55.92; H, 7.12;N, 10.52; S, 4.82; Found: C, 55.95; H, 7.02; N, 10.58; S, 4.62.

(2) Synthesis of H-Tyr-Arg-OH (Kyotorphin)

In 5 ml of trifluoroacetic acid-thioanisole (9:1) was dissolved 300 mgof Boc-Tyr-Arg(Pme)-OH and the mixture was allowed to stand at 50° C.for 4 hours. The trifluoroacetic acid was distilled off under reducedpressure, ether was added to the residue and the resulting precipitatewas collected by filtration. The precipitate was dissolved in a smallamount of water, passed through a column (1×10 cm) of Amberlite IRA-410(acetate-form) and lyophilized. The lyophilizate was dissolved in asmall amount of water, chromatographed on a carboxymethylcellulosecolumn (2.2×8 cm) and eluted by the linear gradient method using water(300 ml) and 0.1 M ammonium acetate (300 ml). The fractions from 110 to155 ml were pooled and lyophilized.

Yield 135 mg, [α]_(D) ²¹ -17.8° (c=0.5, H₂ O); amino acid analysis (acidhydrolysis): Arg 1.00(1), Tyr 0.92(1); average recovery 88.7%.

The desired compound can also be produced using Arg (Tms) or Arg(Tmo) inplace of Arg(Pme). However, in the final step of removing the protectivegroup with trifluoroacetic acid-thioanisole (9:1), it is preferable thatArg(Tms) be treated at 50° C. for 90 minutes and Arg(Tmo) at 50° C. for5 hours.

EXAMPLE 22 (1) Synthesis of Z-Arg(Pme)-Pro-Lys(Boc)-Pro-OH

In 30 ml of methanol was dissolved 0.59 g of oily Z-Pro-Lys(Boc)-Pro-OMeprepared by serial condensation of H-Pro-OMe, Z-Lys(Boc)-ONB andZ-Pro-ONB. Catalytic reduction was then carried out in the presence ofpalladium black as catalyst. The catalyst was filtered off, the filtrateconcentrated and the residue dissolved in 10 ml of dimethylformamide. Tothis solution were added Z-Arg(Pme)-OH [prepared from 0.56 g ofZ-Arg(Pme)-OH.CHA], 0.15 g of HOBt and 0.23 g of DCC. The mixture wasstirred at room temperature for 15 hours. The by-product DCU wasfiltered off and after the solvent was distilled off, the residue wasdissolved in ethyl acetate and washed with aqueous sodium hydrogencarbonate and 0.2 N HCl. After drying, the solvent was distilled off andthe oily residue [Z-Arg(Pme)-Pro-Lys(Boc)-Pro.OMe] was dissolved in 10ml of methanol. Then 2 ml of 1 N-aqueous sodium hydroxide was added inthe cold, and saponification was carried out at room temperature for 2hours. The reaction mixture was neutralized by addition of 2 ml of 1N-hydrochloric acid when cold. After removal of the methanol bydistillation, the resulting oily precipitate was extracted with ethylacetate. The solvent was distilled off, petroleum benzin was added tothe residue and the resulting powder was collected by filtration andreprecipitated from ethyl acetate-ether.

Yield 0.49 g (53.2%), m.p. 92°-96° C., [α]_(D) ²³ -34.4° (c=0.5,dimethylformamide)

Elemental analysis for C₄₄ H₇₂ O₁₁ N₈ S; Calcd.: C, 57.37; H, 7.88; N,12.17; S, 3.48; Found: C, 57.09; H, 7.79; N, 11.86; S, 3.15.

(2) Synthesis ofZ-Arg(Pme)-Pro-Lys(Boc)-Pro-Gln-Gln-Phe-Phe-Gly-Leu-Met-NH₂

In a mixture of trifluoroacetic acid (4.5 ml) and water (0.5 ml) wasdissolved 0.49 g of Boc-Gln-Gln-Phe-Phe-Gly-Leu-Met-NH₂ and the mixturewas shaken at 10° C. for 20 minutes. After addition of 0.5 ml of 1N-hydrochloric acid, the reaction mixture is distilled. Ether was addedto the residue and the resulting powder was collected by filtration anddried. The powder was dissolved in 15 ml of dimethylformamide and 0.1 mlof triethylamine was added when cold. Then, 0.45 g ofZ-Arg(Pme)-Pro-Lys(Boc)-Pro-OH, 0.18 g of HONB and 0.20 g of DCC wereadded and the mixture was stirred for 24 hours. The formed DCU wasfiltered off and the filtrate was concentrated. To the residue was addedwater and the resulting precipitate was collected by filtration andreprecipitated from ethanol-water.

Yield 0.52 g (55.2%), m.p. 245°-250° C. (decomp.), [α]_(D) ²³ -32.8°(c=0.5, dimethylformamide)

Elemental analysis for C₈₅ H₁₃₀ O₁₉ N₁₈ S₂ ; Calcd.: C, 57.60; H, 7.39;N, 14.23; S, 3.62; Found: C, 57.35; H, 7.48; Nm 14.02; S, 3.39.

(3) Synthesis of H-Arg-Pro-Lys-Pro-Gln-Gln-Phe-Phe-Gly-Leu-Met-NH₂(Substance P)

In 5 ml of trifluoroacetic acid-thioanisole (9:1) was dissolved 100 mgof Z-Arg(Pme)-Pro-Lys(Boc)-Pro-Gln-Gln-Phe-Phe-Gly-Leu-Met-NH₂ and themixture was shaken at 50° C. for 4 hours. The trifluoroacetic acid wasdistilled off under reduced pressure, ether was added to the residue andthe resulting precipitate was collected by filtration and dried. Theprecipitate was dissolved in a small amount of water, passed through acolumn (1×10 cm) of Amberlite IRA-410 (acetate-form) and lyophilized.The lyophilisate was chromatographed on a column (2.5×120 cm) ofSephadex G-25 and eluted with 30% aqueous acetic acid. The fractionsrich in the contemplated compound (235-270 ml) were pooled andlyophilized.

Yield 62 mg, [α]_(D) ²³ -79.6° (c=0.5, 5% acetic acid); amino acidanalysis (acid hydrolysis): Lys 1.00(1), Arg 1.03(1), Gln 2.21(2), Pro2.15(2), Gly 0.95(1), Met 0.91(1), Leu 1.02(1), Phe 1.95(2); averagerecovery 85.6%.

The desired compound can also be produced using Arg (Tms) or Arg(Tmo) inplace of Arg(Pme). However, in the final step of removing the protectivegroup with trifluoroacetic acid-thioanisole (9:1), it is preferable thatArg(Tms) be treated at 50° C. for 90 minutes and Arg(Tmo) at 50° C. for5 hours.

EXAMPLE 23 (1) Synthesis of 2,3,5-trimethylanisole

In 100 ml of DMSO were dissolved 10 g of 2,3,5-trimethylphenol and 10.4ml of methyl iodide. Under ice-cooling, 5.6 g of 60% sodium hydride inoil was added, and the mixture was stirred at room temperature for 10hours. After addition of water, the extraction with ether was carriedout. The ether layer was washed with water and dried over anhydroussodium sulfate. Removal of the solvent by distillation leaves the oilysubstance.

Yield 12.9 g (quantitative)

(2) Synthesis of 4-methoxy-2,3,6-trimethylbenzensulfonyl chloride

In 500 ml of methylenchloride was dissolved 4.5 g of2,3,5-trimethylanisole, and after cooling at -5°˜-10° C., a solution(400 ml) of 6.0 ml of chlorosulfonic acid in methylene chloride wasadded dropwise to the mixture. The reaction mixture was kept at roomtemperature and then poured into ice-5% aqueous NaHCO₃. The methylenechloride layer was washed with water and dried over anhydrous magnesiumsulfate. The solvent was distilled off and the residue was crystallizedfrom n-hexane and filtered.

Yield 5.0 g (67.0%), m.p. 56°-58° C.

Elemental analysis for C₁₀ H₁₃ O₃ SCl; Calcd.: C, 48.29; H, 5.27; S,12.89; Cl 14.26; Found: C, 48.42; H, 5.21; S, 12.61; Cl 14.25.

(3) Synthesis of Z-Arg(Mtr)OH.CHA

In a mixture of 10 ml of 4 N-NaOH and 40 ml of acetone was dissolved2.83 g of Z-Arg-OH and the solution was ice-cooled. A solution (10 ml)of 4.0 g of 4-methoxy-2,3,6-trimethylbenzenesulfonyl chloride in acetonewas addded and the mixture was stirred for three hours. Aqueous citricacid was added, the acetone was distilled off, and the desired productwas extracted with ethyl acetate. Removal of the solvent by distillationleaves 4.8 g of an oily substance. This substance was dissolved in asmall amount of ethyl acetate and was crystallized by addition of 1.04ml of cyclohexylamine. The resulting crystals are recrystallized from amixture of methanol and ethyl acetate.

Yield 4.10 g (72.1%), m.p. 195°-197° C. [α]_(D) ²³ +6.5° c=1.18,methanol)

Elemental Analysis for C₃₀ H₄₅ O₇ N₅ S; Calcd.: C, 58.14; H, 7.32; N,11.30; S, 5.17; Found: C, 58.08; H, 7.34; N, 11.58; S, 5.32.

(4) Synthesis of H-Arg(Mtr)-OH

In 30 ml of ethyl acetate suspended 1.5 g of Z-Arg(Mtr)-OH.CHA, followedby addition of 15 ml of 0.2 N-H₂ SO₄. The mixture was shaken well andwashed with water and the solvent is distilled off. The residue wasdissolved in methanol and catalytic reduction was carried out in thepresence of palladium black as catalyst. The catalyst was filtered offand the solvent is distilled off. To the residue was added water and theresulting crystal was obtained by the filtration.

Yield 0.77 g (81%), m.p. 100°-103° C., [α]_(D) ²³ -4.8° (c=1.30,methanol)

Elemental analysis for C₁₆ H₂₆ O₅ N₄ S.1/2H₂ O; Calcd.: C, 48.59; H,6.88; N, 14.18; S, 8.11; Found: C, 48.78; H, 7.16; N, 13.88; S, 8.29.

Test example

In 2 ml of trifluoroacetic acid-thioanisole (9:1) was dissolved 20 mg ofH-Arg(Mtr)-OH, and the solution is allowed to stand under the conditionsas shown in Table 3. A 100 μl portion of the solution was taken, made upto 10 ml and analyzed for arginine. The results are shown in Table 3.

                  TABLE 3                                                         ______________________________________                                                   Temperature                                                                            Time      Yield of Arg                                               (°C.)                                                                           (hrs.)    (%)                                             ______________________________________                                        H--Arg(Mtr)--OH                                                                            23         0.5       68.3                                                                1         85.4                                                     50         0.5       88.9                                                                1         84.9                                        ______________________________________                                    

As is clear from data of Table 3, Mtr can be easily removed at 23° C.for one hour.

EXAMPLE 24 (1) Synthesis of Boc-Tyr-Arg(Mtr)-OH

In 20 ml of tetrahydrofuran was dissolved 0.80 g of H-Arg(Mtr)-OH. Then,0.34 ml of triethylamine and Boc-Tyr-ONB (prepared from 0.57 g ofBoc-Tyr-OH, 0.40 g of HONB and 0.50 g of DCC) were added in the cold,and the mixture was stirred at room temperature for 15 hours. Thesolvent was distilled off and the residue was made acidic with citricacid and extracted with ethyl acetate. The ethyl acetate layer waswashed with water and the solvent was distilled off. The residue wasdissolved in chloroform and subjected to silica gel column (4×6 cm)chromatography. Elution was carried out with 5% MeOH/CHCl₃. Thefractions containing the desired product were pooled, concentrated andprecipitated from ether and the resulting powder was recovered byfiltration.

Yield 0.6 g (51.5%), m.p. 114°-121° C., [α]_(D) ²³ +1.2° (c=0.4,dimethylformamide)

Elemental analysis for C₃₀ H₄₃ O₉ N₅ S; Calcd.: C, 55.45; H, 6.67; N,10.78; S, 4.94; Found: C, 55.12; H, 6.83; N, 10.53; S, 4.54.

(2) Synthesis of H-Tyr-Arg-OH (Kyotorphin)

In 5 ml of mixed solution of trifluoroacetic acid-thioanisole (9:1) wasdissolved 400 mg of Boc-Tyr-Arg(Mtr)OH and the resulting mixture wasallowed to stand at room temperature for 2 hours. The trifluoroaceticacid was distilled off under reduced pressure, ether was added to theresidue and the resulting precipitate was collected by filtration. Theprecipitate was dissolved in a small amount of water, passed through acolumn (1×10 cm) of Amberlite IRA-410 (acetate-form) and lyophilized.The lyophilizate was dissolved in a small amount of water,chromatographed on a carboxymethyl-cellulose column (2.2×8 cm) andeluted by the linear gradient method using water (300 ml) and 0.1 Mammonium acetate (300 ml). The fractions from 100 to 150 ml were pooledand lyophilized. Yield 175 mg, [α]_(D) ²¹ -17.4° (c=0.5, H₂ O); aminoacid analysis (acid hydrolysis): Arg 1.00(1), Tyr 0.94(1); averagerecovery 86.5%.

EXAMPLE 25 (1) Synthesis of Z-Arg(Mtr)-Pro-Lys(Boc)-Pro-OH

In 30 ml of methanol was dissolved 0.59 g of oily Z-Pro-Lys(Boc)-Pro-OMeprepared by serial condensation of H-Pro-OMe, Z-Lys(Boc)-ONB andZ-Pro-ONB. Catalytic reduction was then carried out in the presence ofpalladium black as catalyst. The catalyst was filtered off, the filtrateconcentrated and the residue dissolved in 10 ml of dimethylformamide. Tothis solution were added Z-Arg(Mtr)-OH [prepared from 0.56 g ofZ-Arg(Mtr)-OH.CHA], 0.15 g of HOBt and 0.23 g of DCC. The mixture wasstirred at room temperature for 15 hours. The by-product DCU wasfiltered off and after the solvent was distilled off, the residue wasdissolved in ethyl acetate and washed with aqueous sodium hydrogencarbonate and 0.2 N HCl. After drying, the solvent was distilled off andthe oily residue [Z-Arg(Mtr)-Pro-Lys(Boc)-Pro.OMe] was dissolved in 10ml of methanol. Then 2 ml of 1 N-aqueous sodium hydroxide was added inthe cold, and saponification was carried out at room temperature for 2hours. The reaction mixture was neutralized by addition of 2 ml of 1N-hydrochloric acid when cold. After removal of the methanol bydistillation, the resulting oily precipitate was extracted with ethylacetate. The solvent was distilled off, petroleum benzin was added tothe residue and the resulting powder was collected by filtration andreprecipitated from ethyl acetate-ether.

Yield 610 mg(66.1%), m.p. 90°-95° C., [α]_(D) ²³ -32.7° (c=0.5,dimethylformamide)

Elemental analysis for C₄₃ H₇₀ O₁₂ N₈ S; Calcd.: C, 55.94; H, 7.64; N,12.14; S, 3.47; Found: C, 55.62; H, 7.86; N, 11.98; S, 3.19.

(2) Synthesis of H-Arg-Pro-Lys-Pro-Gln-Gln-Phe-Phe-Gly-Leu-Met-NH₂(Substance P)

In a mixture of trifluoroacetic acid (4.5 ml) and water (0.5 ml) wasdissolved 0.49 g of Boc-Gln-Gln-Phe-Phe-Gly-Leu-Met-NH₂ and the mixturewas shaken at 10° C. for 20 minutes. After addition of 0.5 ml of 1N-hydrochloric acid, the reaction mixture was distilled. Ether was addedto the residue and the resulting powder was collected by filtration anddried. The powder was dissolved in 15 ml of dimethylformamide and 0.1 mlof triethylamine was added when cold. Then, 0.45 g ofZ-Arg(Mtr)-Pro-Lys(Boc)-Pro-OH, 0.18 g of HONB and 0.20 g of DCC wereadded and the mixture was stirred for 24 hours. The formed DCU wasfiltered off and the filtrate was concentrated. To the residue was addedwater and the resulting precipitate was collected by filtration. 100 mgof the precipitate was dissolved in 1 ml of mixed solution oftrifluoroacetic acid-thioanisole (9:1), and shaken at 50° C. for onehour. The trifluoroacetic acid was distilled off under reduced pressure,ether was added to the residue and the resulting precipitate wascollected by filtration and dried. The precipitate was dissolved in asmall amount of water, passed through a column (1×10 cm) of AmberliteIRA-410 (acetate-form) and lyophilized. The lyophilisate waschromatographed on a column (2.5×120 cm) of Sephadex G-25 and elutedwith 30% aqueous acetic acid. The fractions rich in the contemplatedcompound (230-260 ml) were pooled and lyophilized.

Yield 58 mg, [α]_(D) ²³ -78.8° (c=0.5, 5% acetic acid); amino acidanalysis (acid hydrolysis): Lys 1.00(1), Arg 1.04(1), Gln 2.05(2), Pro2.20(2); Gly 0.91(1), Met 0.89(1), Leu 1.05(1), Phe 1.89(2): averagerecovery 82.3%.

What we claim is:
 1. In a method of producing a peptide containing aguanidino group which comprises protecting the guanidino group of aguanidino-containing starting compound with a protecting group,subjecting the protected compound to a peptide synthesis reaction andremoving the protective group with an acid, the improvement wherein theprotecting group is a substituted benzenesulfonyl group of the formula##STR4## wherein R₁, R₃ and R₅ are methyl or methoxy, and R₂ and R₄ arehydrogen or methyl, provided that (1) when R₃ is methyl, all of R₁, R₂,R₄ and R₅ are methyl, (2) when R₃ is methoxy and R₂ and R₄ are bothhydrogen, R₁ and R₅ are both methoxy and (3) when R₃ is methoxy R₁ andR₅ are both methyl, R₂ is hydrogen or methyl and R₄ is hydrogen ormethyl.
 2. The method as claimed in claim 1, wherein the substitutedbenzenesulfonyl group is 4-methoxy-2,6-dimethylbenzenesulfonyl group. 3.The method as claimed in claim 1, wherein the substitutedbenzenesulfonyl group is pentamethylbenzenesulfonyl group.
 4. The methodas claimed in claim 1, wherein the substituted benzenesulfonyl group is4-methoxy-2,3,6-trimethylbenzenesulfonyl group.
 5. The method as claimedin claim 1, wherein the acid is trifluoroacetic acid.
 6. The method asclaimed in claim 1, wherein the removal of the protective group iseffected in the presence of thioanisole.
 7. A compound of the formula##STR5## wherein R₁, R₃ and R₅ are methyl or methoxy, and R₂ and R₄ arehydrogen or methyl, provided that (1) when R₃ is methyl, all of R₁, R₂,R₄ and R₅ are methyl, (2) when R₃ is methoxy and R₂ and R₄ are bothhydrogen, R₁ and R₅ are both methoxy, and (3) when R₃ is methoxy and R₁and R₅ are both methyl, R₂ is hydrogen or methyl and R₄ is hydrogen ormethyl, and R₆ is hydrogen or an α-amino-protecting group.
 8. Thecompound as claimed in claim 7, wherein R₁ and R₅ are methyl, R₂ and R₄are hydrogen and R₃ is methoxy.
 9. The compound as claimed in claim 7,wherein R₁, R₂, R₃, R₄ and R₅ are methyl.
 10. The compound as claimed inclaim 7, wherein R₁, R₂ and R₅ are methyl, R₃ is methoxy and R₄ ishydrogen.